: How does something become radioactive?



I stuck on a documentary about Chernobyl, there was a clip of a pair of boots the fireman were wearing near the plant and the levels of radiation went stupidly high. How can an object like the boots show such a high reading but other objects in the room show lower readings? They also shown a cloth the nurses used on the fireman and the reader did the same thing.

Howcome that happens? Does radiation “stick” to objects?

In: Physics

Radiation is fast particles or high energy photons, it doesn’t get far and it can’t stay around. What made Chernobyl problematic was not radiation directly, it is was the release of radioactive material that distributed in the environment. This radioactive material decays over time, emitting radiation in the process. Just like regular dust gets everywhere you had now dust particles made out of radioactive material that got everywhere. You can clean contaminated objects, but that is an effort that only makes sense if you need the objects again.

Edit: thank you much for the award!!

“Radiation” here is the energy and particles released from radioactive material.

What you’re describing is *contamination* – radioactive material in unwanted/bad places. It’s usually just in the form of a powder, like sand or granulated sugar.

If you have a chunk of uranium, then it’s putting out energy. If you scrape some of that off on to a pizza, now you’ve got uranium on the pizza and the pizza is contaminated.

Radiation comes from radioactive particles.

Like literally microscopic pieces of dust carrying radioactive material.

So things like clothing, which are very porous, are good and absorbing a lot of that dust and material. Thus there’s radioactive material stuck in the the clothing making the clothing radioactive.

Less porous materials like, say, a rock, don’t hold onto that radio active material as well so you don’t see as much an effect.

Radioactivity comes from radioactive isotopes, such as cesium-137 (half-life 30 years). If these stick to porous materials such as leather or cloth, it may be hard to wash them off. And probably not worth the trouble.

Was it Ben Fogle In Chernobyl? Lol

Neuron radiation can activate (make radioactive) certain materials.

Basically a neutron ejected from a decaying atom can end up wedged in another atom. This can cause the previously stable nucleus to become unstable, and thus will undergo radioactive decay at some point in the future.

Edit: I think I got carried away because physics is fun.

tl;dr/more ELI5: Radiation isn’t sticky. Things that emit radiation is sticky because they can be moved around easily by wind and contact. When things come into contact with these things, it is then hard to clean off. If things are not directly subjected to these radioactive things, then they will emit less radiation.

To help understand this, I’ll help define “radiation” first. Radiation in this context refers to all 3 types, named after the first 3 letters of the Greek alphabet: alpha, beta, and gamma. Each are physically different things, and so have different properties when interacting with other matter. There’s also radiation in the form of neutrons, but they’re not *too* different when it comes to this discussion.

Briefly, alpha radiation are ionized helium atoms, beta radiation are electrons, or their anti-matter counterpart, positrons, and gamma radiation is high-energy “light” (electromagnetic waves). All three types are typically labelled as “ionizing radiation” because they contain enough energy to bump into other matter and strip off electrons (to ionize the target atom). This is why ionizing radiation is dangerous, because it will likely cause whatever it comes into contact with to deteriorate in some manner.

Radioactive things are ultimately things that result in these types of radiation, and come from unstable versions of elements (i.e. radioactive isotopes). Because these unstable elements tend to decay and break apart, they release radiation and daughter atoms that may also be unstable themselves, thus causing a chain event of radioactivity.

Now more towards your question. This ability for the detectors to detect radiation levels depends on the amount of ionizing radiation present. The detectors are called Geiger counters (unless there are also other detectors, I’m not a nuclear physics expert), and measure how much stuff inside the detector is being ionized, and correlate that to a level of radiation that would cause that.

So what do we have so far? We have many types of radiation, coming from radioactive elements, which can be detected by Geiger counters. In your example, the boots have a significantly higher radiation reading because they were at reactor trying to put out the fire. As a result, they were subjected to a lot of the crap blown out by the explosion, and were covered/mixed with these radioactive elements. These radioactive elements will then emit radiation, probably in all 3 forms, and is then detected by the Geiger counter.

The room however, was not directly subjected to the dust resulting from the explosion, and thus has less radioactive elements covering the objects in that room. However, this does not mean that it was not subjected it to radiation at all, because there is still the presence of highly-penetrating gamma radiation.

So with that, “radiation” does not stick to objects, it is usually the radioactive elements. These elements are then carried by things that *do* stick to objects, like cement dust, and can result in being rather “sticky” since it cannot be “killed” like a microbe, and all you can really do is wash it off mechanically, or let it decay until it is no longer radioactive. This also helps understand why nuclear fallout is dangerous, because the radioactive materials (effectively “dust”) that come out of an explosion can travel quite far by wind.